Osteoarthritis is a degenerative process in joints characterized by functional deterioration, abrasion of articular cartilage, and formation of new bone at and around the joint surfaces. It is estimated to affect approximately 40 million adults in the United States alone. The disease is particularly prevalent in individuals over the age of 55 and with the longevity of the population increasing, it has become a disease of major concern to the medical community.
In humans, osteoarthritis takes years to develop. As the disease progresses, the affected diseased cartilage literally wears away. At the present time, osteoarthritis cannot be diagnosed until quite late in the degenerative process. Current medical treatment therefore consists mainly of trying to reverse the later inflammatory stage of the disease. At this point, it is really too late to stop or reverse the degenerative process.
It has long been acknowledged in the literature that the events leading up to these late inflammatory stages are the most important. Many drug companies have for example given up the idea of treating osteoarthritis with anti-inflammatory drugs and are now trying to discover and develop drugs that will treat the primary lesion or the early stages of the disease. However, assays to monitor the effectiveness of these drugs on the early stages of osteoarthritis are not available. Moreover, diagnosis of the disease in its early stages has also not been possible. Therefore, in a clinical setting, it cannot be determined which patients are affected by the disease in its earliest stages and thus, are candidates for such drugs and therapies.
U.S. Pat. No. 4,704,356 refers to a potential marker for diagnosing osteoarthritis. It employs a quantitative immunoassay for keratan sulfate, which is thought to be elevated in patients with osteoarthritis. This immunoassay is not satisfactory for the diagnosis of osteoarthritis. First, it detects an increased release of a normal tissue component without selectively identifying a pathological process. More importantly, there is still much controversy in the field over whether the initial stages of the degenerative process are associated with an abnormally high or an abnormally low level of keratan sulfate. Finally, the method of the '356 patent is useful only prospectively, i.e., to confirm the presence of osteoarthritis. It has not been used to diagnose or track the disease in its earliest stages.
As a result, clinical assessment of osteoarthritis is hampered by the lack of sound diagnostic criteria and the absence of means to detect and measure the active processes of joint damage. Because the disease is widespread, heterogeneous and slowly progressive, the need for definitive and reliable tests is paramount not only for diagnosis, but also for longitudinal assessment, epidemiology and drug development.